1. Field of the Invention
The present invention relates to sealed pushbutton switches for use on printed circuit boards, and in particular to a single pole, normally closed switch having an O-ring that prevents leaks between an actuator and cover of the switch without significantly changing the actuation force, and having an epoxy sealed base.
2. Description of Related Art
Pushbutton switches that are soldered into printed circuit boards can be contaminated after going through soldering precesses and cleaning processes. If an external seal is provided, the manufacturer must remove the seal after processing. External seals add material and labor costs.
O-rings have been used with switches, for example, to keep a switch water tight. The following U.S. Patents disclose the use of O-rings in switches:
U.S. Pat. No. 2,748,229 issued to Edwin H. Block on May 29, 1954 and assigned to the United States of America discloses a cam operated water tight switch operated by depressing a plunger. In order to insure a water tight connection between casing and wall, a ring of solder is heat sealed in grooves and in the casing. The switch comprises the plunger having a pushbutton slidably mounted in a bore. An O-ring gasket is mounted in a groove of the plunger for preventing ingress of water to the interior of the switch casing. The plunger has a threaded extension and a tubular member and a hollow cylindrical plug. A pair of micro switches, having operating pins are operated by spring arms extending from a member having a cam surface when the plunger is moved inwardly. A spring returns tubular member to the initial position and springs are released by cam surfaces. However, this invention uses an O-ring in a manner that significantly affects actuation force.
U.S. Pat. No. 3,983,354 issued Sep. 28, 1976 to Joseph E. Gammie et al. and assigned to General Motors Corporation discloses a rotary switch comprising a housing, a cover, three stationary contacts, a rotor, an O-ring seal and a combination sealing and driving member. The switch is used to arm and disarm an automobile anti-theft system in response to operation of the door lock key. However, this invention also uses an O-ring in a manner that significantly affects actuation force.
U.S. Pat. No. 5,389,758, issued Feb. 14, 1995 to William J. Agnatovech and assigned to Augat, Inc. discloses a miniature pushbutton switch manufactured of molded, resilient parts that are snap-fitted together. The switch comprises a platform assembly, a pushbutton assembly and an encasement assembly. No tools are required to assemble the switch and glue or epoxy may be used to seal the switch. The pushbutton assembly comprises a pushbutton actuator, a bias element or spring 52 and a slider block having at least one electrical shorting element disposed therein and in electrical contact with one set of contacts. However, this invention does not have an O-ring seal.
Accordingly, it is therefore an object of this invention to provide a sealed pushbutton switch with terminals for soldering onto a printed circuit board.
It is another object of this invention to provide a pushbutton switch that is sealed and suitable for undergoing soldering processes and cleaning processes.
It is a further object of this invention to provide a sealed single pole, normally closed pushbutton switch having an epoxy seal on the bottom of the switch.
It is another object of this invention to provide a sealed pushbutton switch having an O-ring on an actuator to prevent leaks between the actuator and a cover of the switch without changing the actuation force.
It is another object of this invention to provide a sealed pushbutton switch that is easily and quickly assembled at low cost.
These and other objects are accomplished by a sealed pushbutton switch comprising a cover having an opening in one side of the cover, an actuator having a shaft portion and a head portion, the shaft portion extending through the opening in the side of the cover, the shaft having an annular groove adjacent to the head portion, means positioned between the head portion of the actuator and a side of the cover opposite the side with the opening for maintaining the actuator in a normally closed position, means disposed in the annular recess of the actuator for making a seal between the actuator and the cover, a base having first and second terminals inserted into channels on opposite sides of the base, a contact spring disposed within the head portion of the actuator, a first end and a second end of the contact spring contacting a top portion of the first and second terminals in the base, when the pushbutton switch is in a normally closed position, the cover being attached to the base, and means for sealing a bottom surface of the base adjacent to the cover and the terminals extending from the bottom of the base. The means for maintaining the actuator in a normally closed position comprises a spring. The means disposed in the annular recess for making a seal comprises an O-ring. The means for sealing a bottom surface of the base comprises an epoxy. The epoxy seals between the base and the cover and around the terminals extending from the base.
The objects are further accomplished by a method of providing a sealed pushbutton switch comprising the steps of providing a cover having an opening in one side of the cover, extending through the opening in the side of the cover, an actuator having a shaft portion and a head portion, the shaft portion having an annular groove adjacent to the head portion, maintaining the actuator in a normally closed position with means positioned between the head portion of the actuator and a side of the cover opposite the side with the opening, making a seal between the actuator and the cover with means disposed in the annular groove of the actuator, providing a base having first and second terminals inserted into channels on opposite sides of the base, disposing a contact spring within the head portion of the actuator, a first end and a second end of the contact spring contacting a top portion of the first and second terminals in the base, when the pushbutton switch is in a normally closed position, attaching the cover to the base, and sealing a bottom surface of the base adjacent to the cover and the terminals extending from the bottom of the base. The step of maintaining the actuator in a normally closed position comprises the step of providing a spring positioned between the head portion of the actuator and a side of the cover. The step of making a seal between the actuator and the cover comprises the step of providing an O-ring within the annular groove. The step of sealing a bottom surface of the base comprises the step of using an epoxy to accomplish the sealing. The step of using the epoxy comprises the step of placing the epoxy between the base and the cover and around the terminals extending from the base.
Additional objects, features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of the preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.